(b) Engines. Lessee may return the Aircraft on the Return Occasion with an engine not owned by Lessor, so long as (i) such engine conforms in all respects to the requirements set forth in Section 11(b) hereof with respect to a Replacement Engine; (ii) such engine conforms to the return condition requirements set forth in Subsections 16(d) and 16(f) hereof; and (iii) Lessee, at its own expense and concurrently with such delivery, furnishes Lessor with a warranty bill of sale, in form and substance reasonably satisfactory to Lessor, with respect to such engine and with evidence of Lessee's full and unencumbered title to such engine (including, if requested, an opinion of Lessee's counsel to the effect of the opinion required by Section 11(b)(iv) hereof) and Lessee takes such other action as Lessor may reasonably request in order that full legal and beneficial ownership and title to such engine shall be duly and fully vested in Lessor; provided however, that there shall be no substitution of an engine for an Engine such that the time and cycles remaining on any Replacement Engine is less than the time and cycles that were remaining on the replaced Engine based upon actual hours / cycles operated by Lessee. Lessee's obligation to comply with the terms of this Subsection 16(c) shall be conditioned on the Lessor's transferring to Lessee full legal and beneficial ownership and title to any Engine not installed on the Aircraft at the Return Occasion, without any representation, warranty or recourse of any kind whatsoever, express or implied, except a warranty that such Engine is free and clear of Liens, other than Liens which Lessee is required to discharge hereunder.